This invention pertains to the growth and maintenance of plants in hydroponic devices.
The hydroponic cultivation of crops has received only limited acceptance as an alternative to conventional farming. Commercial growers consider a hydroponic installation feasible only for high profit crops which will immediately return the high initial investment in the greenhouse and growing system. And in the consumer market, despite the resurging popularity of home gardening in response to the upward spiral in food prices, again, the relative high cost of the devices offered by manufacturers against the low value of the vegetables and flowers produced has limited the acceptance of hydroponics. These high costs are not inherent to hydroponics, which is the simple feeding of a nutrient solution to the roots of plants grown independently of the soil; rather, the costs are due to the devices now employed by commercial and amateur systems: the expense of the chemically inert medium and the equipment required to contain and support that medium far exceed the cost of the nutrient delievery systems. It is evident, to reduce the costs of hydroponics and thus promote the acceptance of hydroponics in the marketplace, the medium and the devices secondary to the actual nourishment of the growing plants must be eliminated.
It is known that the hydroponic cultivation of plants, in carefully controlled circumstances, requires no medium. In laboratory experiments, when researchers attempt to determine the precise affects of certain chemicals on plants, plants are grown suspended in a vessel, nutrient solution periodicly or incessantly trickling over the bare, but protected, roots. Or the roots float in a vessel filled with nutrient solution, the solution constantly aerated to supply needed oxygen. In these ways, there can be no unknown substances introduced by contaminated medium. However, the fact that a system failure of more than a few hours results in a total crop loss limits the commercial acceptance of the techniques.
A variation of the above-described laboratory process in which the roots are suspended in a protective vessel is the continuous flow technique. In this process, the plant roots lie in channels, the system's nutrient solution continuously flowing over the bare roots. The channels are mounted horizontally on racks, one above another like rungs in a ladder. Pumped solution enters the top channel, flows through each channel, finally draining into a reservoir. Some systems, in an improvement over simply spreading the naked roots over the epoxy-coated aluminum or plastic channels, incorporate fiberous matting at the bottom of the channels. This matting offers a greater area of moisture and nutrients to the roots. But this technique is also subject, though to a lesser degree, to total loss in the event of even a temporary failure in the circulation of the solution. The open channels also present problems: sunlight striking the exposed nutrient solution creates ideal conditions for the growth of airborne micro-organisms; and if the grower attempts to use the system outside of a greenhouse, insects attack the naked roots. It is only with elaborate fabrications that prior inventions have overcome the shortcomings of the technique*. FNT *U.S. Pat. Nos. 3,667,157 Longhini, 4,035,950 Anseim, 4,166,341 Vestergaard.